Is that for an opened bottle or a sealed bottle only, do you know?
The discussion was around sealed bottle sitting on a shelf and that the oil should last at least 5 years from when blended during manufacture and bottling. And it was further elaborated that after the 5 years, if there was no sediment on the bottom of the bottle, then the oil is still ok as all the additives are still in suspension.
We didn’t explicitly discuss shelving opened containers. But oil isn’t bottled in a dry nitrogen filled environment at the factory, so it does get exposed to some air and thus moisture during the bottling process. And as long as a bottle is opened and what’s left after the service is put in a smaller container, so the air within the bottle is minimised, then it’s really not going to go off quicker.
Really in one sense rebottling at home is just like what occurs during manufacturer when oil is poured/pumped from larger containers into smaller containers. So doing the same at home, the oil will continue to keep well for the remainder of the original shelf life …
And even if one doesn’t pour the leftovers into a smaller container, I doubt it would kill the remaining oil any quicker. After all, it’s the passage of time where suspended additives could settle that’s the issue and in service heat cycle and contamination from combustion that really kills oil. It’s not a few litres of air trapped in a bottle after opening and recapping that causes problems … heck I’ve even kept opened brake fluid bottles for years and not had issues (though I do use insulation tape around the bottle’s cap)
